Convert between decimal inches, fractional inches, millimetres, and centimetres with selectable fraction precision from 1/2 to 1/64.
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Measurement Conversion
An inch fraction calculator converts between decimal inches, fractional inches, and millimetres. It is used in woodworking, machining, and construction where plans and measurements may use different precision formats that need to be reconciled.
A decimal inch value is converted to the nearest fraction at the selected precision (1/2, 1/4, 1/8, 1/16, 1/32, or 1/64). The calculator rounds to the closest available fraction and shows the fractional and decimal equivalents side by side.
Millimetre and centimetre equivalents are also provided so the measurement can be used with metric tools and drawings.
Millimetres = Inches x 25.4
One inch equals exactly 25.4 millimetres.
Woodworkers converting between tape-measure fractions and digital caliper readings, machinists converting between imperial blueprints and metric tooling, and builders reconciling plans drawn in different units all use this type of conversion regularly.
Frequently asked questions
Multiply the decimal portion by the denominator you want (for example, 16 for sixteenths), round to the nearest whole number, and place it over the denominator. This calculator does that automatically.
One inch equals exactly 25.4 millimetres.
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